The computer

virtual reality and 3D interaction

positioning in 3D spacemoving and grasping

seeing 3D (helmets and caves)

Positioning in 3D space• cockpit and virtual controls

– Used by Aircraft pilots, PC games – steering wheels, knobs and dials … just like real!

• the 3D mouse– Move in 3 dimensions-forward, backward and rotation – six-degrees of movement: x, y, z + roll, pitch, yaw

• data glove– fibre optics used to detect finger position– Used for gesture recognition, sign language interpretation

• VR helmets– They display 3D world to each eye– detect head motion and manipulation of object

• whole body tracking– accelerometers strapped to limbs or reflective dots and video processing– Game have motorbike body on with you can lean into curves

pitch, yaw and roll

pitch

yaw

roll

3D displays

• desktop VR– ordinary screen, mouse or keyboard control– perspective and motion give 3D effect

• seeing in 3D– use stereoscopic vision– VR helmets– screen plus shuttered specs, etc.

VR headsets

• small TV screen for each eye• slightly different angles• 3D effect

VR motion sickness

• time delay– move head … interval … display moves– conflict: head movement vs. eyes

• depth perception– headset gives different stereo distance– but all focused in same plane– conflict: eye angle vs. focus

• conflicting cues => sickness– helps motivate improvements in technology

Simulators and VR caves• scenes projected on

walls• realistic environment• hydraulic rams!• real controls• VR rooms having large

displays positioned all around the user is called caves

physical controls, sensors etc.

special displays and gaugessound, touch, feel, smell

physical controlsenvironmental and bio-sensing

Dedicated displays

• analogue representations:– dials, gauges, lights, etc.

• digital displays:– small LCD screens, LED lights, etc.

• head-up displays – found in aircraft cockpits– show most important controls

Sounds

• Beeps, bongs, clonks, whistles and whirrs are used to varying effect

• Used for error indications (alerts)• Confirmation of actions e.g. Keyclick• Telephone keypads sound different tones

Touch, feel, smell

• touch and feeling important– in games … vibration, force feedback– in simulation … feel of surgical instruments– called haptic devices– Braille displays have pins that rise or fall to give

different patterns• texture, smell, taste

– current technology very limited

BMW iDrive

• for controlling menus• feel small ‘bumps’ for each item• makes it easier to select options by feel • uses haptic technology from Immersion Corp.

physical controls

• specialist controls needed …– industrial controls, consumer products, etc.

large buttonsclear dials

tiny buttons

multi-functioncontrol

easy-cleansmooth buttons

Environment and bio-sensing

• sensors all around us– car courtesy light – small switch on door– ultrasound detectors – security, washbasins– RFID security tags in shops– temperature, weight, location – Wash basins

• … and even our own bodies …– iris scanners, body temperature, heart rate, galvanic

skin response, blink rate

paper: printing and scanning

print technologyfonts, page description, WYSIWYG

scanning, OCR

Printing

• image made from small dots– allows any character set or graphic to be printed,

• critical features:– resolution

• size and spacing of the dots• measured in dots per inch (dpi)

– speed• usually measured in pages per minute

– cost!!

Types of dot-based printers• dot-matrix printers

– use inked ribbon (like a typewriter– line of pins that can strike the ribbon, dotting the paper.– typical resolution 80-120 dpi

• ink-jet and bubble-jet printers– tiny blobs of ink sent from print head to paper– typically 300 dpi or better .

• laser printer– like photocopier: dots of electrostatic charge deposited on drum,

which picks up toner (black powder form of ink) rolled onto paper which is then fixed with heat

– typically 600 dpi or better.

Printing in the workplace

• shop tills– dot matrix– same print head used for several paper rolls– also print cheques

• thermal printers– special heat-sensitive paper– paper heated by pins makes a dot– poor quality, but simple & low maintenance– used in some fax machines

Fonts• Font – the particular style of text

Courier font Helvetica font Palatino font

Times Roman font• §´ ¿   ¿~ µº Â Ä (special symbol)

• Size of a font measured in points (1 pt about 1/72”)(vaguely) related to its height

This is ten point Helvetica This is twelve point

This is fourteen point This is eighteen point

and this is twenty-four point

Fonts (contd.)

Pitch– fixed-pitch – every character has the same width

  e.g. Courier– variable-pitched – some characters wider

  e.g. Times Roman – compare the ‘i’ and the “m”

Serif or Sans-serif– sans-serif – square-ended strokes

  e.g. Helvetica

– serif – with splayed ends (such as)  e.g. Times Roman or Palatino

Readability of text

• lowercase– easy to read shape of words

• UPPERCASE– better for individual letters and non-words

e.g. flight numbers: BA793 vs. ba793

• serif fonts– helps your eye on long lines of printed text– but sans serif often better on screen

Page Description Languages

• Pages very complex– different fonts, bitmaps, lines, digitised photos, etc.

• Can convert it all into a bitmap and send to the printer

• Alternatively Use a page description language– sends a description of the page can be sent,– instructions for curves, lines, text in different styles, etc.– like a programming language for printing!

• PostScript is the most common

Screen and page

• WYSIWYG– what you see is what you get– aim of word processing, etc.

• but …– screen: 72 dpi, landscape image– print: 600+ dpi, portrait

• can try to make them similarbut never quite the same

• so … need different designs, graphics etc, for screen and print

Scanners

• Take paper and convert it into a bitmap

• Two sorts of scanner– flat-bed: paper placed on a glass plate, whole page converted into

bitmap– hand-held: scanner passed over paper, digitising strip typically 3-4”

wide

• Shines light at paper and note intensity of reflection– colour or greyscale

• Typical resolutions from 600–2400 dpi

Scanners (ctd)

Used in

– desktop publishing for incorporating photographs and other images

– document storage and retrieval systems, doing away with paper storage

+ special scanners for slides and photographic negatives

Optical character recognition

• OCR converts bitmap back into text• different fonts

– create problems for simple “template matching” algorithms

– more complex systems segment text, decompose it into lines and arcs, and decipher characters that way

• page format– columns, pictures, headers and footers

Paper-based interaction• paper usually regarded as output only

• can be input too – OCR, scanning, etc.

• Xerox PaperWorks– glyphs – small patterns of /\\//\\\

• used to identify forms etc.• used with scanner and fax to control applications

• more recently– papers micro printed - like wattermarks

• identify which sheet and where you are– special ‘pen’ can read locations

• know where they are writing

Memory

short term and long termspeed, capacity, compression

formats, access

Short-term Memory - RAM• Random access memory (RAM)

– on silicon chips– 100 nano-second access time– usually volatile (lose information if power turned off)– data transferred at around 100 Mbytes/sec

• Some non-volatile RAM used to store basic set-up information

• Typical desktop computers:64 to 256 Mbytes RAM

Long-term Memory - disks• magnetic disks

– floppy disks store around 1.4 Mbytes– hard disks typically 40 Gbytes to 100s of Gbytes

access time ~10ms, transfer rate 100kbytes/s

• optical disks– use lasers to read and sometimes write– more robust that magnetic media– CD-ROM

- same technology as home audio, ~ 600 Gbytes– DVD - for AV applications, or very large files

Blurring boundaries

• PDAs– often use RAM for their main memory

• Flash-Memory– used in PDAs, cameras etc.– silicon based but persistent– plug-in USB devices for data transfer

Virtual memory• Problem:

– running lots of programs + each program large– not enough RAM

• Solution - Virtual memory :– store some programs temporarily on disk– makes RAM appear bigger

• But … exchanging– program on disk needs to run again– copied from disk to RAM– s l o w s t h i n g s d o w n

Compression• reduce amount of storage required• lossless

– recover exact text or image – e.g. GIF, ZIP– look for commonalities:

• text: AAAAAAAAAABBBBBCCCCCCCC 10A5B8C• video: compare successive frames and store change

• lossy– recover something like original – e.g. JPEG, MP3– exploit perception

• JPEG: lose rapid changes and some colour• MP3: reduce accuracy of drowned out notes

Storage formats - text

• ASCII - 7-bit binary code for to each letter and character

• UTF-8 - 8-bit encoding of 16 bit character set

• RTF (rich text format)– text plus formatting and layout information

• SGML (standardized generalised markup language)- documents regarded as structured objects

• XML (extended markup language)– simpler version of SGML for web applications

Storage formats - media• Images:

– many storage formats :(PostScript, GIFF, JPEG, TIFF, PICT, etc.)

– plus different compression techniques(to reduce their storage requirements)

• Audio/Video– again lots of formats :

(QuickTime, MPEG, WAV, etc.)– compression even more important– also ‘streaming’ formats for network delivery

Methods of Access

• large information store– long time to search => use index– what you index -> what you can access

• simple index needs exact match• forgiving systems:

– Xerox “do what I mean” (DWIM)– SOUNDEX – McCloud ~ MacCleod– Not used in some cases like ATM

• access without structure …– free text indexing (all the words in a document)– needs lots of space!!

Processing and networks

finite speed (but also Moore’s law)

limits of interactionnetworked computing

Finite processing speed• Designers tend to assume fast processors, and make

interfaces more and more complicated

• But problems occur, because processing cannot keep up with all the tasks it needs to do– cursor overshooting because system has buffered keypresses– icon wars - user clicks on icon, nothing happens, clicks on another,

then system responds and windows fly everywhere

• Also problems if system is too fast - e.g. help screens may scroll through text much too rapidly to be read

Moore’s law• computers get faster and faster!• 1965 …

– Gordon Moore, co-founder of Intel, noticed a pattern– processor speed doubles every 18 months– PC … 1987: 1.5 Mhz, 2002: 1.5 GHz

• similar pattern for memory– but doubles every 12 months!!– hard disk … 1991: 20Mbyte : 2002: 30 Gbyte

• baby born today– record all sound and vision– by 70 all life’s memories stored in a grain of dust!

Limitations on interactive performance

Computation bound– Computation takes ages, causing frustration for the user

Storage channel bound– Bottleneck in transference of data from disk to memory

Graphics bound– Common bottleneck: updating displays requires a lot of effort -

sometimes helped by adding a graphics co-processor optimised to take on the burden

Network capacity– Many computers networked - shared resources and files, access to

printers etc. - but interactive performance can be reduced by slow network speed

Networked Computing

• Increase interactivity• Operate on large distance and with high speed• Networks allow access to …

– large memory and processing– other people (groupware, email)– shared resources – esp. the web

• Issues– network delays – slow feedback– conflicts - many people update data– unpredictability